NAME:__________________________ DATE:__________SECTION______LAB #
_____
BREAK IT DOWN
In 1899, Ernest Rutherford wrote the following words:
"These experiments show that the uranium radiation is complex
and that there are present at least two distinct types of radiation one that is very readily absorbed, which will be termed for
convenience the alpha-radiation, and the other of more
penetrative character which will be termed the beta-radiation."
The image to the right is of a twenty-eight year old Ernest
Rutherford while at McGill University in 1899.
Alpha (α) decay can most simply be described like this:
1) The nucleus of an atom splits into two parts.
2) One of these parts (the alpha particle) goes zooming off into space.
3) The nucleus left behind has its atomic number reduced by 2 and its mass number
reduced by 4 (that is, by 2 protons and 2 neutrons).
Notice several things about it:
1) The atom on the left side is the one that splits into two pieces.
2) One of the two atoms on the right is ALWAYS an alpha particle.
3) The other atom on the right ALWAYS goes down by two in the atomic number and
four in the mass number.
Beta (β– ) decay is somewhat more complex than alpha decay is. These points present a
simplified view of what beta decay actually is:
1) A neutron inside the nucleus of an atom breaks down, changing into a proton.
2) It emits an electron and an anti-neutrino (more on this later), which go zooming off
into space.
3) The atomic number goes UP by one and mass number remains unchanged.
Here is an example of a beta decay equation:
Some points to be made about the equation:
1) The nuclide that decays is the one on the left-hand side of the equation.
2) The order of the nuclides on the right-hand side can be in any order.
3) The way it is written above is the usual way.
Notice (for both alpha and beta decay) that all the atomic numbers on both sides ADD UP
TO THE SAME VALUE and the same for the mass numbers.
Positron Decay:
Positron (β+ ) decay is like a mirror image of beta decay. These points present a
simplified view of what positron decay actually is:
1) Something inside the nucleus of an atom breaks down, which causes a proton to
become a neutron.
2) The atomic number goes DOWN by one and mass number remains unchanged.
Here is an example of a positron decay equation:
Some points to be made about the equation:
1) The nuclide that decays is the one on the left-hand side of the equation.
2) The order of the nuclides on the right-hand side can be in any order.
3) The way it is written above is the usual way.
4) The mass number and atomic number of the neutrino are zero.
Electron Capture:
Electron capture is not like any other decay - alpha, beta, or position. All other decays
shoot something out of the nucleus. In electron capture, something ENTERS the nucleus.
These points present a simplified view of what electron capture is:
1) An electron from the closest energy level falls into the nucleus, which causes a proton
to become a neutron.
2) Another electron falls into the empty energy level and so on causing a cascade of
electrons falling. One free electron, moving about in space, falls into the outermost
empty level.
3) The atomic number goes DOWN by one and mass number remains unchanged.
Here is an example of a electron capture equation:
Some points to be made about the equation:
1) The nuclide that decays is the one on the left-hand side of the equation.
2) The electron must also be written on the left-hand side.
3) The way it is written above is the usual way.
Gamma Decay:
Gamma rays (γ) are high-energy photons emitted from atomic nuclei.
After alpha or beta emission, some daughter nuclei have excess energy, and they become
stable after emission of gamma photons. Thus, gamma rays are emitted almost at the
same time beta or alpha rays are emitted.
60
Co 
60
Ni + -e + γ
Nuclei not releasing the excess energy immediately are called isomers, which are
represented by a superscript m following the mass number. These isomers emit gamma
rays.
Tc 
99m
Tc + γ
99
PURPOSE:
1) To investigate the different change that unstable nuclei can undergo.
2) To use the periodic table to aid in writing nuclear equations.
PROCEDURE:
For the following radioactive isotopes show the results of each decay.
A) Alpha Decay
239
Pu
B) Beta Decay
60
Co
C) Alpha Decay
87
Kr
D) Gamma Decay
52m
Mn
E) Alpha Decay
235
U
F) Beta Decay
90
Sr
G) Positron Decay
50
Mn
H) Beta Decay
16
N
I) Positron Decay
15
O
J) Alpha Deacy
186
Os
L) Electron Capture
38
Ar
M) Electron Capture
73
As
3) Show the intial radioactive isotope:
A) Beta Decay
X

0
e–1 +
101
Tc43

4
He2 +
233
Pa91
B) Alpha Decay
X
C) Positron Decay
X

0
e+1 +
D) Gamma Decay
X 
γ0 +
0
152
Dy66
4) Fill in the missing particle
A)
237
Np93  _____+
235
Pa91
B)
_______ 0e+1 +
18
O8
C)
203
Hg80 0e–1 + ______
D)
57
Co27 + _______
57
Fe26
8
Be4
E)
239
Cm96 + ____________
239
Am95
Reflection:
Describe what occurs to the mass number and atomic number of during each type of
decay.
Describe the method used to determine the idenity of the missing radioisotope in a
nuclear equation.